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All about: Methoxsalen

Big Image Pronouncation: (meth-OX-ah-len)
Class: Psoralen

Trade Names:
8-MOP
- Capsules 10 mg

Trade Names:
Oxsoralen-Ultra
- Capsules, soft gelatin 10 mg

Trade Names:
Oxsoralen
- Lotion 1% (10 mg/mL)

Trade Names:
Uvadex
- Solution 20 mcg/mL

Mechanism of Action

Pharmacology

Exact mechanism not known; however, methoxsalen acts as a photosensitizer.

Pharmacokinetics

Absorption

8-MOP

Max bioavailability is reached 1.5 to 3 h after oral administration and lasts up to 8 h.

Oxsoralen-Ultra

Reaches peak blood drug levels in 0.5 to 4 h, and detectable levels are observed up to 12 h.

Distribution

Methoxsalen is reversibly bound to serum albumin and preferentially taken up by epidermal cells.

Metabolism

Methoxsalen is rapidly metabolized.

Elimination

Approximately 95% is excreted as a series of metabolites in the urine within 24 h.

Oxsoralen-Ultra

The t ½ is approximately 2 h.

Duration

Oxsoralen-Ultra

Time of peak photosensitivity is 1.5 to 2.1 h.

Indications and Usage

Symptomatic control of severe, recalcitrant, disabling psoriasis not responsive to other forms of therapy and when diagnosis supported by biopsy ( Oxsoralen-Ultra , 8-MOP capsule); use in conjunction with long wave UV radiation for repigmentation of idiopathic vitiligo ( 8-MOP capsule, Oxsoralen lotion); with long wave UV radiation of white blood cells (photopheresis) with the UVAR Photopheresis System in the palliative treatment of skin manifestations of cutaneous T-cell lymphoma in people not responsive to other forms of treatment ( 8-MOP capsule, Oxsoralen lotion); extracorporeal administration with UVAR Photopheresis System in the palliative treatment of skin manifestation of cutaneous T-cell lymphoma that is unresponsive to other forms of treatment ( Uvadex solution).

Contraindications

Patients exhibiting idiosyncratic reactions to psoralen compounds; specific history of light-sensitive disease states should not initiate methoxsalen therapy (eg, lupus erythematosus, porphyria cutanea tarda, erythropoietic protoporphyria, variegate porphyria, xeroderma pigmentosum, albinism); patients exhibiting melanoma or possessing a history of melanoma; patients exhibiting invasive squamous cell carcinomas; patients with aphakia, because of increased risk of retinal damage caused by absence of lenses.

Dosage and Administration

Vitiligo
Adults 8-MOP

PO Take 20 mg daily in 1 dose with milk or food 2 to 4 h prior to UV exposure. Take on alternate days and never on 2 consecutive days. Sun exposure is based on basic skin color. Initial sun exposure should be 15 min for light skin, 20 min for medium-colored skin, and 25 min for dark skin. The second, third, and fourth exposures may be increased by 5 min/each exposure (if basic skin color is light, the second exposure can be increased to 20 min, the third exposure to 25 min, and the fourth exposure to 30 min). Subsequent exposures may gradually be increased based on erythema and tenderness of amelanotic skin (max, 0.6 mg/kg).

Oxsoralen lotion

Apply lotion to a small, well-defined, vitiliginous lesion, then expose this area to UVA light. Initial exposure time must not exceed one half the minimal erythema dose. Regulate treatment intervals by erythema response (once weekly or less, depending on the results). Pigmentation may begin after a few weeks; significant repigmentation may take up to 6 to 9 mo. Periodic treatment may be needed to retain the new pigmentation.

Psoriasis
Adults Oxsoralen-Ultra

PO Take with food or milk 1.5 to 2 h prior to UVA exposure.

8-MOP

PO Take with food or milk 2 h prior to UVA exposure. Take according to the following recommendations: Generally, elderly patients should be started at the low end of the dose recommended according to body weight and closely monitored during PUVA therapy. No treatments should be given more often than once every other day because the full extent of phototoxic reactions may not be evident until 48 h after each exposure. Dosage may be increased by 10 mg after the fifteenth treatment. Patients weighing:

  • Less than 30 kg take 10 mg
  • 30 to 50 kg take 20 mg
  • 51 to 65 kg take 30 mg
  • 66 to 80 kg take 40 mg
  • 81 to 90 kg take 50 mg
  • 91 to 115 kg take 60 mg
  • Greater than 115 kg take 70 mg
Cutaneous T-Cell Lymphoma
Adults Uvadex

Extracorporeal with the UVAR Photopheresis System only. (Not for parenteral administration.) Normal treatment schedule: Treatment is given on 2 consecutive days q 4 wk for a minimum of 7 treatment cycles (6 mo). Accelerated treatment schedule: If assessment of the patient during the fourth treatment cycle (approximately 3 mo) reveals an increased skin score from the baseline score, the frequency of treatment may be increased to 2 consecutive treatments q 2 wk. If a 25% improvement in the skin score is attained after 4 consecutive wk, the regular treatment schedule may be resumed (max, 20 cycles). Consult UVAR Photopheresis System Operator's Manual before using this product. Treatment involves collection of leukocytes, photoactivation, and reinfusion of photoactivated cells. During each photopheresis treatment, 200 mcg (10 mL) of Uvadex is injected directly into photoactivation bag during the first buffy coat collection cycle. At the end of 6 cycles, a total of 740 mL (240 mL of buffy coat, 300 mL of plasma, and 200 mL of normal saline priming fluid) is collected and mixed with the 200 mcg of Uvadex present in the photoactivation bag. After photoactivation, the cells are reinfused.

Storage/Stability

Store at controlled room temperature (59° to 86°F).

Drug Interactions

Known photosensitizers (eg, anthralin, coal tar, coal tar derivatives, fluoroquinolone antibiotics, griseofulvin, halogenated salicylanilides, nalidixic acid, organic staining dyes [eg, methylene blue, methyl orange, rose bengal, toluidine blue], phenothiazines, sulfonamides, tetracyclines, thiazide diuretics)

Exercise care when using these agents and methoxsalen concurrently.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

8-MOP , Oxsoralen-Ultra

Hypotension.

Uvadex

Hypotension (secondary to extracorporeal volume [greater than 1%]).

CNS

8-MOP , Oxsoralen-Ultra

Dizziness; headache, malaise, depression.

Dermatologic

8-MOP , Oxsoralen-Ultra

Pruritus (10%); erythema; hypopigmentation; vesiculation and bullae formation; nonspecific rash; urticaria; folliculitis; cutaneous tenderness; extension of psoriasis.

GI

8-MOP , Oxsoralen-Ultra

Nausea (10%); GI disturbances.

Miscellaneous

8-MOP , Oxsoralen-Ultra

Edema; herpes simplex; miliaria; leg cramps.

Uvadex

Infection.

Precautions

Warnings

Methoxsalen should only be used by physicians who have special competence in the diagnosis and treatment of psoriasis and vitiligo ( 8-MOP , Oxsoralen-Ultra ) or cutaneous T-cell lymphoma ( Uvadex ) and who have special training and experience in photochemotherapy. 8-MOP may not be interchanged with Oxsoralen-Ultra capsules without retitration of the patient. Oxsoralen-Ultra has greater bioavailability and earlier photosensitization onset time than previous forms. Fully inform patient the possibilities of ocular damage, aging of the skin, and skin cancer.


Pregnancy

Category C ( 8-MOP , Oxsoralen-Ultra ); Category D ( Uvadex ).

Lactation

Undetermined.

Children

Safety and efficacy not established.

Elderly

Use with caution, start at low end of dosing range.

Hepatic Function

Because hepatic biotransformation is necessary for drug urinary excretion, use with caution.

Carcinogenesis

Risk of squamous cell carcinoma among PUVA-treated patients is increased (especially in patients who are fair-skinned or have had pre-PUVA exposure to prolonged tar and UVB treatment) ionizing radiation, or arsenic. Risk of basal cell carcinoma may also be increased.

Special Risk Patients

Diligently observe and treat patients with basal cell carcinoma or a history of basal cell carcinoma; diligently observe patients with a history of previous x-ray therapy, grenz ray therapy, or arsenic therapy for signs of carcinoma; patients with cardiac disease or others who may be unable to tolerate prolonged standing or exposure to heat stress should not be treated in a vertical UVA chamber.

Actinic degeneration

Exposure to sunlight and/or UV radiation may result in premature aging of the skin.

Cataract

Because the concentration of methoxsalen in the lens is proportional to the serum level, if the lens is exposed to UVA while methoxsalen is present, photochemical action may lead to irreversible binding of the methoxsalen to proteins and DNA components of the lens.

Sunbathing

The presence of sunburn may prevent the accurate evaluation of the patient's response to photochemotherapy.

Total dosage

Total cumulative dose of UVA that can be given safely over long periods of time has not been established.

Patient Information

  • Advise patient that response to therapy is not rapid and that it may take weeks to months to achieve ma benefit.
  • Advise patient that ingesting limes, figs, parsley, parsnips, mustard, carrots, or celery might cause an exaggerated response to the UVA treatments or the sun and to ingest carefully until tolerance is determined.
  • Capsules
  • Advise patient to read the Patient Package Insert before starting therapy and with each refill.
  • Advise patient that nausea is a common side effect and to take each dose with food or milk to minimize this problem. If nausea still occurs advise patient to divide the dose into 2 portions taken approximately 30 min apart with food or milk.
  • Caution patient to take the dose exactly as prescribed and to carefully follow the timing recommendations between taking the dose and starting the UVA treatment. Advise patient that serious burns can result if drug dosing schedules and/or UVA exposure schedules are not followed.
  • Instruct patient to wear UVA-absorbing, wraparound sunglasses for the 24-h period following ingestion of methoxsalen, whether exposed to direct or indirect sunlight outside or through a glass window.
  • Caution patient not to sunbathe during the 24 h prior to and 48 h after taking methoxsalen and UVA treatment.
  • Caution patient to avoid exposure to sunlamps and the sun, even through windows or cloud cover, for at least 8 h after taking methoxsalen. If sun exposure cannot be avoided, instruct patient to wear protective devices (eg, hat, gloves), and/or apply sunscreen that filters out UVA radiation (“UVA protection”) with a sun protective factor (SPF) of 15 or greater. Instruct patient to apply sunscreen to all areas that might be exposed to the sun, including lips, but not to apply until after the UVA treatment.
  • Advise patient that if itching occurs in UVA-treated areas to frequently apply a bland emollient. If itching persists or worsens, advise patient to notify health care provider.
  • Advise patient to frequently examine their skin for small growths or sores that do not heal. Instruct patient to inform health care immediately if noted.
  • Advise patient to notify health care provider if nausea, itching, redness, tenderness, or blistering of skin occurs and lasts more than 24 to 48 h.
  • Lotion
  • Advise patient that lotion will be applied by a health care provider in a health care setting before undergoing UVA treatment.
  • Instruct patient to keep the treated areas protected from sunlight by wearing protective clothing or applying a sunscreen with UVA protection and a sun protection factor (SPF) of 15 or greater. Advise patient that the area of application may be highly sensitive to sunlight or sunlamps for several days after application.
  • Solution
  • Advise that blood will be drawn and sent to the lab where this medication will be used to treat the patient's white blood cells. Once the treatment has been completed, the treated white blood cells will be returned to their body.
  • Instruct patient to wear UVA-absorbing, wraparound sunglasses and cover exposed skin or use a sunblock with UVA protection and an SPF of 15 or greater for the 24-h period following treatment of blood cells.

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